Plant instrumentation devices such as temperature sensors, pressure transducers and weighing instruments require regular calibration to ensure they are performing and measuring to specified tolerances.
However, different companies use very different methods of managing these calibrations. These methods differ greatly in terms of cost, quality, efficiency, and accuracy of data and their level of automation.
Calibration software is one tool that can be used to support and guide calibration management activities, with documentation being a critical part of this.
But in order to understand how software can help process plants better manage their instrument calibrations, it is important to consider the typical calibration management tasks that companies have to undertake. There are five main areas are: planning and decision-making, organisation, execution, documentation, and analysis.
Documentation is a very important part of a calibration management process. ISO 9001:2000 and the FDA both state that calibration records must be maintained and that calibration must be carried out according to written, approved procedures.
This means an instrument engineer can spend as much as 50 per cent of his or her time on documentation and paperwork – time that could be better spent on other value-added activities. This paperwork typically involves preparing calibration instructions to help field engineers; making notes of calibration results in the field; and documenting and archiving calibration data.
Imagine how long and difficult a task this is if the plant has thousands of instruments that require calibrating on at least a six-monthly basis? The amount of manual documentation increases almost exponentially.
Volume of documentation
When it comes to the volume of documentation required, different industry sectors have different requirements and regulations. In the power and energy sector, for example, just under a third of companies (with 500+ employees) typically have more than 5,000 instruments that require calibrating.
Forty-two per cent of companies perform more than 2,000 calibrations each year. In the highly regulated pharmaceuticals sector, a massive 75 per cent of companies carry out more than 2,000 calibrations per year.
Oil, gas and petrochemicals sector is similarly high, with 55 per cent of companies performing more than 2,000 calibrations each year. The percentage is still quite high in the food and beverage sector, where 21 per cent of firms said they calibrated their instruments more than 2,000 times every year.
The figures outlined appear to suggest that companies really do require some sort of software tool to help them manage their instrument calibration processes and all associated documentation. However, the picture in reality can be very different.
In a Beamex Calibration Study carried out in 2007, a mere 25 per cent of companies with 500+ employees (across the industry sectors mentioned above) said that they did use specialist calibration management software.
Many other companies said that they relied on generic spreadsheets and/or databases for this, whilst others used a calibration module within an existing Computerised Maintenance Management System (CMMS). A significant proportion (almost 20 per cent) of those surveyed said they used a manual, paper-based system.
Any type of paper-based calibration system will be prone to human error. Noting down calibration results by hand in the field and then transferring these results into a spreadsheet back at the office may seem archaic, but many firms still do this.
Furthermore, analysis of paper-based systems and spreadsheets can be almost impossible, let alone time consuming.
Historical trend analysis
In a recent survey conducted by Control Magazine, 40 per cent of companies surveyed said that they calculated calibration intervals by using historical trend analysis – which is encouraging. However, many of these firms said they were doing it without any sort of calibration software to assist them.
The other 60 per cent of companies determined instrument calibration intervals based on either the manufacturer’s own recommendation, or they used a uniform interval across the plant for all instruments.
Neither method is ideal in practice. Companies could save so much time and reduce costs by using calibration management software to analyse historical trends and calibration results.
Using software for calibration management enables faster, easier and more accurate analysis of calibration records and identifying historical trends. Plants can therefore reduce costs and optimise calibration intervals by reducing calibration frequency when this is possible, or by increasing the frequency where necessary.
For example, for improved safety, a process plant may find it necessary to increase the frequency of some sensors that are located in a hazardous, potentially explosive area of the manufacturing plant.
Just as important, by analysing the calibration history of a flow meter that is located in a ‘non-critical’ area of the plant, the company may be able to decrease the frequency of calibration, saving time and resources.
Rather than rely on the manufacturer’s recommendation for calibration intervals, the plant may be able to extend these intervals by looking closely at historical trends provided by calibration management software.
Instrument ‘drift’ can be monitored closely over a period of time and then decisions taken confidently with respect to amending the calibration interval. Regardless of industry sector, there seems to be some general challenges that companies face when it comes to calibration management.
The number of instruments and the total number of periodic calibrations that these devices require can be several thousand per year.
How to plan and keep track of each instrument’s calibration procedures means that planning and scheduling is important. Furthermore, every instrument calibration has to be documented and these documents need to be easily accessible for audit purposes.
These systems typically involve hand-written documents. Typically, this might include engineers using pen and paper to record calibration results while out in the field. On returning to the office, these notes are then tidied up or transferred to another paper document, after which they are archived as paper documents.
While using a manual, paper-based system requires little or no investment, it is very labour-intensive and means that historical trend analysis becomes very difficult to carry out. In addition, the calibration data is not easily accessible.
The system is time consuming, soaks up a lot of resources and typing errors are commonplace. Dual effort and re-keying of calibration data are also significant costs here.
Although certainly a step in the right direction, using an in-house legacy system to manage calibrations has its drawbacks. In these systems, calibration data is typically entered manually into a spreadsheet or database.
The data is stored in electronic format, but the recording of calibration information is still time-consuming and typing errors are common. Also, the calibration process itself cannot be automated. For example, automatic alarms cannot be set up on instruments that are due for calibration.
CMMS calibration module
Many plants have already invested in a Computerised Maintenance Management (CMM) system and so continue to use this for calibration management. Plant hierarchy and works orders can be stored in the CMM system, but the calibration cannot be automated because the system is not able to communicate with ‘smart’ calibrators.
Furthermore, CMM systems are not designed to manage calibrations and so often only provide the minimum calibration functionality, such as the scheduling of tasks and entry of calibration results.
Although instrument data can be stored and managed efficiently in the plant’s database, the level of automation is still low. In addition, the CMM system may not meet the regulatory requirements for managing calibration records.
With specialist calibration management software, users are provided with an easy-to-use Windows Explorer-like interface. The software manages and stores all instrument and calibration data.
This includes the planning and scheduling of calibration work; analysis and optimisation of calibration frequency; production of reports, certificates and labels; communication with smart calibrators; and easy integration with CMM systems such as SAP and Maximo.
With software-based calibration management, planning and decision-making are improved. Procedures and calibration strategies can be planned and all calibration assets managed by the software. Position, device and calibrator databases are maintained, while automatic alerts for scheduled calibrations can be set up.
Analysis becomes easier too, enabling engineers to optimise calibration intervals using the software’s History Trend function. Also, when a plant is being audited, calibration software can facilitate both the preparation and the audit itself.
Locating records and verifying that the system works is effortless when compared to traditional calibration record keeping.
[Reproduced with permission from "Ultimate Calibration" by Beamex Oy Ab. Beamex products are distributed in Australia by AMS Instrumentation & Calibration.]